Injection molding apparatus and method

Abstract

The present invention is directed to an injection molding apparatus and method capable of preventing the occurrence of over-packing. The apparatus includes a pair of dies for forming a plurality of cavities therebetween; die closing devices for closing the pair of dies under a prescribed pressure; an injection device for injecting a molten resin into respective cavities under a prescribed pressure; and, a control device for controlling the die closing devices and the injection device. Further, the apparatus comprises a plurality of pressure sensors for detecting respective pressures in respective cavities and a control device that controls the injection device and/or the die closing devices to reduce the rate of injection of the molten resin and/or the force of closing the dies and, otherwise, stops the injection and/or the die closing operation when the pressure difference between cavities is found to be greater than a prescribed value on the basis of sensed values from the respective pressure sensors.

1. An injection molding method utilizing an injection molding apparatus having at least a pair of dies that are openable and closable for forming a plurality of cavities therebetween when said pair of dies are closed, into which a molten resin is injected, said method comprising the steps of:
 detecting the pressure in each of said plurality of cavities, respectively; and  
 when a pressure difference between said plurality of cavities exceeds a predetermined value, reducing the rate of injection of the molten resin and/or the die closing force.  
 
     
     
       2. An injection molding method utilizing an injection molding apparatus having at least a pair of dies that are openable and closable for forming a plurality of cavities therebetween when said pair of dies are closed, into which a molten resin is injected, said method comprising the steps of:
 detecting the pressure in each of said plurality of cavities, respectively; and when a pressure difference between said plurality of cavities exceeds a predetermined value, stopping injection of the molten resin and/or application of a die closing force.  
 
     
     
       3. An injection molding apparatus, comprising:
 at least a pair of dies that are openable and closable for forming a plurality of cavities therebetween when said pair of dies are closed;  
 die closing means for closing said pair of dies under a prescribed pressure;  
 injection means for injecting a molten resin under a prescribed pressure into said plurality of cavities formed between said pair of dies when said dies are closed;  
 control means for controlling said die closing means and said injection means; and  
 a plurality of pressure detection means for detecting pressure in each of said plurality of cavities, wherein:  
 said control means controls said injection means and said die closing means in accordance with a detected value from said plurality of pressure detection means,  
 wherein when a pressure difference among said plurality of cavities is found to be greater than a prescribed value, said control means controls the rate of injection of the molten resin and/or the die closing force to be reduced, in accordance with the detected values from said plurality of pressure detection means.  
 
     
     
       4. An injection molding apparatus, comprising:
 at least a pair of dies that are openable and closable for forming a plurality of cavities therebetween when said pair of dies are closed;  
 die closing means for closing said pair of dies under a prescribed pressure;  
 injection means for injecting a molten resin under a prescribed pressure into said plurality of cavities formed between said pair of dies when said dies are closed;  
 control means for controlling said die closing means and said injection means; and  
 a plurality of pressure detection means for detecting pressure in each of said plurality of cavities, wherein:  
 said control means controls said injection means and said die closing means in accordance with a detected value from said plurality of pressure detection means,  
 wherein when a pressure difference among said plurality of cavities is found to be greater than a prescribed value, said control means stops the injection of the molten resin and/or application of a die closing force, in accordance with the detected values from said plurality of pressure detection means.  
 
     
     
       5. The injection molding apparatus according to any one of claims  3  or  4 , wherein said control means carries out its control in accordance with a program which presets injection conditions at a first molding in an injection molding operation. 
     
     
       6. The injection molding apparatus according to any one of claims  3  or  4 , wherein said control means controls the quantity of injection of the molten resin in a first molding instance in its injection molding operation becomes 1/n or less compared with a quantity of injection thereof in a second and subsequent molding instances, provided that there exist n cavities.